Wave-signal receiver including duplex frequency-changer stages



p 3 N. P. CASE WAYE'SIGNAL RECEIVER INCLUDING DUPLEX FREQUENCY-CHANGER STAGES Filed July 5. 1940 my 5 2% u INVENTOR NELSON F? CASE ATTORNEY Patented Aug. 5, 1941 UNITED STATES PATENT, OFFICE WAVE-SIGNAL RECEIVER INCLUDING DU- PLEX FREQUENCY-CHAN GER STAGES Nelson P. Case, Great Neck, N. Y., assignor to Hazcltine Corporation, a corporation of Delaware .Claims.

Application July 5, 1940, Serial No. 343,939

perheterodyne type, two different intermediate- 7 frequency carrier signals are provided by means of two modulators or frequency changers in the signal-translating channel of the receiver. Vacuum-tube repeaters have heretofore commonly been utilized to repeat or to amplify two or more signals of substantially different frequencies. Such devices have been utilized to provide a reflex amplification of a signal in a modulatedcarrier signal receiver, thus to minimize the number of tubes required to provide a desired gain. For example, such reflex amplifier stages have been utilized to effect a dual amplification of an audio-frequency signal and a carrier-frequency signal or, in the case of a superheterodyne receiver, to effect an amplification of an intermediate-frequency signal and a radio-frequency signal. It is, however, desirable to provide a receiver including a duplex frequency-changing stage for the reason that the advantages of a multiple superheterodyne receiver are then provided by the use of a fewer number of frequencychanging stages in the receiver. It has heretofore been proposed to effect a reflex amplification in a modulator or frequency-changer stage. However, no prior art modulated-carrier signal receiver has been provided wherein a plurality of frequency changes have been" effected in the same signal-translating channel and in the same signal-translating stage.

It is an object of the invention, therefore, to provide an improved modulated-carrier signal receiver adapted to effect a plurality of frequency changes of a received signal in the same signaltranslating stage.

In accordance with the invention, a modulatedcarrier signal receiver comprises a carrier-signal frequency-converting stage, including one or more input circuits and a given number of output circuits, means for selecting and applying a desired received carrier signal to one of the input circuits of the stage, and means for apply ing to one of the input circuits of the stage oscillations of a frequency having a predetermined relation to that of the selected signal for heterodyning with the selected signal. There is also provided means for deriving from the heterodyne components so produced an intermediate-frequency carrier signal together with means for feeding back the intermediate-frequency carrier signal to one of the input circuits of the stage and for producing in one of the output circuits of the stage another intermediate-frequency carrier signal. Means are further provided for translating'and reproducing the above-mentioned other intermediate-frequency carrier signal.

For a better understanding of the invention,-

together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

The single figure of the drawing illustrates a frequency-modulation carrier-signal receiver of the multiple superheterodyne type incorporating duplex frequency-changer stages in accordance with the invention.

In general, the receiver represented in the drawing comprises a tunable radio-frequency selector circuit including an inductance l0 and a tuning condenser ll coupled to an inductance l2 of an antenna-ground circuit and to a carrierfrequency signal-translating or frequency-converting stage comprising a multielectrode tube I 3. Tube I3 is of the duplex oscillator-mixer type and the signal input to the receiver is applied to the third grid or outer control electrode of the mixer section of the tube. The carrierfrequency signal-translating stage also includes therein a means for applying to one of the input circuits of the stage ,or for developing in the stage oscillations of a predetermined frequency having a predetermined relation to that of the selected carrier frequency for heterodyning with the selected signal. This means is shown as comprising an oscillator circuit associated with tube l3 and includes a frequency-determining circuit comprising an inductance 41 and a tuning condenser 48, which is unicontrolled with condenser II, as indicated by the dotted line U, for tuning the receiver. producing sustained oscillations in frequencydetermining circuit 41, 48 is provided by the screen grid and the cathode of tube l3. The direct current required by the screen grid is obtained through a resistor 54, while the carriersignal path for this element includes the isolat ing condenser 49 and the tuned circuit 41, 48. The cathode of tube I3 is connected to a tap on inductance 41.

A suitable feed-back circuit for The first intermediate-frequency signal produced by tube l3 in the output circuit thereof is applied through a suitable selector including a double-tuned transformer 56, 52 and 5|, 53 to the third grid or outer control electrode of a second frequency-changer tube 20. The second frequency-changer stage includes means for applying thereto or developing therein oscillations of a predetermined frequency for heterodyning with the first intermediate-frequency signal supplied thereto through selector 50, 52 and 5|, 53. This means comprises an oscillator section in tube 23 having a fixed frequency-determining circuit including an inductance 2| and an adjustably-fixed condenser 22 and having a feed-back circuit therefor provided by the connection of the cathode of tube 20 to a tap on inductance 2|, the oscillator voltage across the circuit 2|, 22 being applied to the first grid or inner control electrode of tube 20 by means of a coupling condenser 23.

A second intermediate-frequency signal is'developed by the heterodyning of the oscillations supplied by the oscillator section of tube 20 and the first intermediate-frequency signal supplied through selector circuit 50, 52 and 5|, 53. This second intermediate-frequency signal is fed back to tube l3 for a further change in frequency. through a selective circuit in the anode of tube 20 which includes an inductance 24 tuned by condenser 25 and inductively coupled to an inductance 26 in the circuit of the outer control electrode of tube l3, inductance 26 being tuned by a condenser 21.

In order to effect the second frequency change in tube l3, a separate source of fixed-frequency oscillations is provided. This source comprises an oscillator section within tube |3 including a frequency-determining circuit comprising an inductance H and adjustably-fixed condensers I5 and 55. A suitable feed-back circuit for developing sustained oscillations in the circuit l4, I5, 55 is provided by connecting the anode of the oscillator section of tube l3 to feedback winding l6 inductively coupled to inductance I4.

The third intermediate-frequency signal so produced from the heterodyne components of the signals just mentioned is translated to tube 20 for a further frequency change through selector circuit 50, 52 and 5|, 53. Transformer 50, 5| is tuned by condensers 52, 53 to a. frequency approximately mid way between the carrier frequencies of the two intermediate-frequency signal outputs of tube l3. Transformer 50, 5| is over-coupled to provide resonant peaks substantially at the carrier frequencies of each of the intermediate-frequency signals to be coupled between tubes l3 and 20.

A fourth intermediate-frequency signal is thus developed by the heterodyne components of the third intermediate-frequency signal translated by selector 50, 52 and 5|, 53 and the source of oscillations provided by the oscillator section of vacuum tube 20. This fourth intermediate-frequency signal is applied to the input circuit of a limiter 35 through a selective circuit in (the anode circuit of vacuum tube 29 including an inductance 36 tuned by a condenser 31 and inductively coupled to an inductance 38, tuned by condenser 39. The fourth intermediate-frequency signal supplied to limiter 35 is therein limited to a substantially constant amplitude to eliminate amplitude-modulation components and is supplied to a frequency-modulation detector 46 wherein the modulation components of the received signal are derived. The audio-frequency components are further amplified by an amplifier 4| and reproduced by a sound reproducer 42. While it is not intended to limit the circuit of the drawing to any specific circuit constants, there follows a set of circuit values which have been found satisfactory for use in a frequencymodulation receiver:

Tube 13 Type 6K8 Tube 20 Type 68A? R. l". Selector circuit 10,

11 Tunable over the range from 42-50 megacycles Oscillator frequency-determining circuit 47, 48 Tunable over the range from 33-41 megacycles mining circuit 14, 15, 55

First and third I. F. Transformer 50, 51

Tuned to the frequency of 1.6 megacycles Tuned to a frequency of 6.8 megacycles and overcoupled to provide new mince peaks at 9 me acycles and 5.1 megacy es Oscillator frequency-determining circuit 21, 22;" Tuned to a frequency of 2.3 megacycles I.\F. transformer 8 Tuned to a frequency of 2.8 megacycles In considering the operation of the circuit of the drawing, it will be seen that a desired received signal within the frequency range from 39 to 45 megacycles is selected by circuit HI, H and is heterodyned in tube l3 with oscillations developed by the tunable oscillator associated with frequency-determining circuit 41, 48 to develop a first intermediate-frequency signal having a carrier frequency of 9 megacycles, which is translated through transformer 50, 5| to tube 20. This first intermediate-frequency signal is heterodyned in tube 20 with the oscillations generated by the oscillator section of this tube to develop a second intermediate-frequency signal having a carrier frequency of 6.7 megacycles which, in turn, is fed back through transformer 24, 26 to tube l3. This second intermediate-frequency signal is heterodyned in tube |3 with the oscillations generated in the oscillator section of the tube connected to frequency-determining circuit |4, I5, 55 to develop a third intermediate frequency signal having a carrier frequency of-5.l megacycles which, in turn, is translated through transformer 50; 5| to tube 25. This third intermediate-frequency signal is heterodyned in tube 20, with the oscillations generated by the oscillator section of this tube to develop a fourth intermediate-frequency signal having a carrier frequency of 2.8 megacycles which is translated through transformer 36, 36 to limiter 35 andthe succeeding stages of the receiver for reproduction in a manner well understood in the art.

It will thus be seen that means are provided for driving from the heterodyne components produced in the output circuit of tube |3 an intermediate-frequency signal which is fed back to tube III for a further frequency change, thereby to produce in the output circuit of tube |3 another intermediate-frequency signal. This feed-back signal is derived indirectly through the succeeding frequency changer 20. Similarly there is derived from the heterodyne components of tube 20 an intermediate frequency signal which is subjected to a later frequency change in tube 20; that is, the signal reflexed to tube 23 for a further frequency change is indirectly derived from heterodyne components of tube 20 through the frequency changer l3.

Fun rth While there have been described what are at present considered to be the preferred embodiments, of this invention. it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention. and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A modulated-carrier signal receiver comprising, a carrier-signal frequency-converting stage including one or more input circuits and a given number of output circuits, means for selecting and applying a desired received carrier signal to one of said input circuits, means for applying to one of said input circuits oscillations of a frequency having a predetermined relation to that of said selected signal for heterodyning with said selected signal, means for deriving from the heterodyne components so produced in one of said output circuits an intermediate-frequency carrier signal, means for feeding back said intermediate-frequency carrier signal to one of said input circuits and for producing in one of said output circuits another intermediate-frequency carrier signal. and means for translating and reproducing said other intermediate-frequency carrier signal.

2. A modulated'carrier signal receiver comprising, a carrier-signal frequency-converting stage including one or more input circuits and a given number of output circuits. means for selecting and applying a desired received signal to one of said input circuits, means for applying to one of said input circuits oscillations oi a frequency having a predetermined relation to that of said selected signal for heterodyning with said selected signal, means for deriving from the heterodyne components so produced in one of said output circuits an intermediate-frequency carrier signal, means for feeding back said intermediate-irequency carrier signal to one of said input circuits, means for applying oscillations of a predetermined frequency to one of said input circuits for heterodyning with said feed-back signal to produce in one of said output circuits another intermediate-frequency carrier signal, and means for translating and reproducing said other intermediate-frequency carrier signal.

3. A modulated-carrier signal receiver comprising, a carrier-signal frequency-converting stage including one or more input circuits and a given number of output circuits, means for selecting and applying a desired received signal to one of said input circuits, means for applying to one of said input circuits oscillations of a frequency having a predetermined relation to that of said selected signal for heterodyning with said selected signal to provide a first intermediate-frequency carrier signal, a second carrier-signal frequencyconverting stage having one or more input circuits and an output circuit, means for applying oscillations of a predetermined frequency to one of said input circuits of said second stage for heterodyning with said first intermediate-frequency carrier signal to provide a second intermediate-frequency carrier signal in said output circuit of said second stage, means for feeding back said second intermediate-frequency carrier signal to one of said input circuits of said first-mentioned stage and for producing in one of said output circuits of said first-mentioned stage a third intermediate-frequency carrier signal, and means for translating and reproducing said third intermediate-frequency carrier signal.

4. A modulated-carrier signal receiver comprising, a first carrier-signal frequency-converting stage including one or more input circuits and a given number of output circuits. means for selecting and applying a desired received signal to one of said input circuits, means for applying to one of said input circuits oscillations of a frequency having a predetermined relation to that of said selected signal for heterodyning with said selected signal, a second carrier-signal frequencyconvertlng stage having one or more input circuits and an output circuit, means for applying said first intermediate-frequency carrier signal to one of said input circuits of said second stage, means for applying oscillations of a predetermined frequency to one of said input circuits of said second stage for heterodyning with said first intermediate-frequency carrier signal to produce a second intermediate-frequency can'ier signal in said output circuit of said second stage, means for feeding back said second intermediate-frequency carrier signal to one of said input circuits of said first stage, a separate source of oscillations of a predetermined frequency, means for applying said last-mentioned oscillations to said first stage for heterodyning with one of said input circuits of said feed-back signal to produce in one of said output circuits of said first stage another intermediate-frequency carrier signal. and means for translating and reproducing said other intermediate-frequency carrier signal.

5. A modulated-carrier signal receiver comprising, a carrier-signal frequency-converting stage including one or more input circuits and a given number of output circuits, means for selecting and applying a desired received signal to one of said input circuits, means for applying to one of said input circuits oscillations of a frequency having a predetermined relation to that of said selected signal for heterodyning with said selected signal, means including a double-tuned overcoupled transformer for selecting from the heterodyne components so produced a first intermediate-frequency carrier signal, means responsive to said intermediate-frequency carrier signal for feeding energy back to one of said input circuits of said stage and for producing in one of said output circuits another intermediate-frequency carrier signal, means including said transformer for selectively translating said other intermediate-frequency carrier signal, said transformer being tuned between the carrier frequencies of said one and said other intermediatefrequency signals and having resonance peaks substantially coinciding with said carrier frequencies, and means for translating and reproducing said other intermediate-frequency carrier signal.

NELSON P. CASE.

CERTIFICATE or conmzcnon. Patent No. 2,251,597. August5, 19in.

maxsour. CASE.

It is hereby certified that error appears in the printed sbecification of the above numbered patent requiring correction as follows: Page 5, second column, lines 55 and56, claim 14., strike out "one of said input circuits of" and insert the same after "to" in line 51+, same (:1 81m; and that the said Letters Patent shouldbe read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed. this law day of November, A. n. 19in.

Henry Van Arsdale,.

(Seal) Acting Commissioner of Patent s. 

